Changing Antifreeze on Yanmar

The below advice, from Mack Boring, is for the Yanmar 3GM30F, but is essentially the same procedure for most engines:

“Coolant Change – Yanmar 3GM30FC (Japan, circa 1999)Coolant Change – Yanmar 3GM30FC (Japan, circa 1999)


Yanmar accepts the following antifreeze applications in their products, present and past models:

  • Ethylene glycol-Changed annually regardless of hours of operation.
  • Extended Life Antifreeze or Coolant (Meets or exceeds ASTM D3306 & D4985) Changed every two years or 250 hours whichever comes first.
  • Yanmar Ultralife YG30
  • Dex-Cool Long Lfe Coolant
  • Havoline Extended Life Antifreeze

Benefits of extended life coolants:

  • reduces hard scale build up
  • better heat transfer
  • no phosphate or silicate formation
  • long term corrosion protection for aluminum, bronze and cast iron
  • improved water pump life

Thomas J. Watts
Technical Support, Mack Boring & Parts Company
908-964-0700 ext. 286


Equipment List:

  • 0.5 gal Dexcool-type Extended Life Antifreeze (ex. Prestone 5yr/150000mi)
    Or 1

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